Abstract: The present invention relates to a method for protecting a payment terminal, comprising: —a data encryption key; —a monitoring module comprising a means for measuring a physical parameter; —a counter unit of a microcontroller, the counter unit being slaved to a clock for incrementing a counter value; said method comprising the steps of: —measuring a physical parameter by the means for measuring the monitoring device; comparing the measured value with a predetermined threshold value corresponding to a physical attack; —resetting the counter unit; and if one of the following conditions is met: ?at least one physical parameter value is indicative of a physical attack on said terminal; ?the counter value is greater than a predefined threshold value; the method also comprises a step of removing access to the encryption key.